But Verizon Wireless, the mobile venture of Verizon, has made no secret of the fact it wants to see a strong third competitor. The biggest U.S. mobile operator has already said it will sell phones based on Microsoft Corp's Windows Phone 8 software later this year to support a third system.

Another contender, Research In Motion, has fallen on hard times and will miss out on 2012 holiday sales as it has delayed its next BlackBerry system until next year. Verizon has also said it wants to sell the next BlackBerry phones when they are ready in early 2013.

Verizon's McAdam said it was too soon to count RIM out of the game and that it was not yet clear which system will win third place going forward.

McAdam said he also expects competition from Samsung, which focuses mostly on selling phones using the Android operating system, after it was recently dealt a bruising defeat in Apple's patent infringement court case against it in California.

"The dark horse here might be Samsung," McAdam said during a webcast of an investor call. "They've got the capability to go out on their own to do their own operating system. They've tinkered with it."

Samsung has developed a mobile operating system called Bada, which it uses for lower-end devices. It uses Android software for its top of the range devices.

However, Charter Equity Research analyst Ed Snyder was skeptical Samsung has a strong Android/iOS rival in the works.

"What (McAdam is) trying to do is stoke the competition," Snyder said.